The Mill Valley home of decor-by-mail retailer Lily Kanter captures her preppy, West Coast style

At the top of a hill in this Northern California town sits a light blue, 19th-century house with a red door, white balconies and a large front porch with a swing. Kids' bicycles lie at the base of terraced gardens. Inside the décor is sunny and crisp, with brightly colored fabrics and wicker chairs.

It looks like a photo from a catalog for California-style living. And that is no accident: This is home...